Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2005
Publication Date: 2/1/2006
Citation: Steenwerth, K.L., Hunt, J.M., Eve, E., Shrestha, A. 2006. Pre-emergent activity of organic herbicides on field bindweed and barnyard grass. Weed Science Society of America Meeting Abstracts.
Technical Abstract: The need for sustainable weed management has increased as growers face enhanced protections for water quality. Essential oils derived from plants and acetic acid represent an alternative weed control method for organic production systems. However, the pre-emergent activity of these herbicides is unknown. To expand the utility of these organic herbicides, we investigated the pre-emergent activity of three essential oils and acetic acid on the seeds of two common vineyard weeds, barnyard grass (Echinocloa crus-gali) and field bindweed (Convolvulus arvensis). Seeds were placed in Petri dishes, and cinnamon oil, clove oil, and acetic acid were applied at rates of 2% and 5%, respectively. Matran5A, a commercially available mix of clove and wintergreen oil, was applied at rates of 5% and 10%. Lecithin was used as an emulsifier with a final solution concentration of 0.1%. Seed viability after treatment was tested with tetrazolium assays. Germination of both species was inhibited by each herbicide. Subsequently, seeds of each species were sown in pots in a greenhouse and the herbicides were sprayed on the soil surface to test their efficacy in a simulated field setting. Concentrations of 5%, 10%, and 20% were applied for clove oil, cinnamon oil, and Matran5A, respectively and concentrations of 5% and 10% were applied for acetic acid. A 0.1% lecithin solution, which was the concentration of the emulsifier in the organic herbicide solutions, and water were applied as controls. The 0.1% lecithin solution suppressed germination of barnyard grass, and a 20% solution of Matran5A inhibited germination of bindweed. These results show that the organic herbicides suppress germination when applied directly to the seeds, but that the method of delivery in the field must be modified to increase their pre-emergent efficacy in the soil.